Question

A bulb is connected first with dc and then ac of same voltage then it will shine brightly with(a) AC(b) DC(c) Brightness will be in ratio 1/1.4(d) Equally with both

Answer 1

answer : option (d) equally with both

explanation : We know, consumption of power of appliance is inversely to the resistance of appliance.

e.g., $P_{consumed}\propto\frac{1}{R}$

but resistance of bulb is constant for both alternating current and direct current. it doesn't change.
e.g., $R_{ac}=R_{dc}$

so, $P_{consumed}$ in alternating current = $P_{consumed}$ in direct current.

hence, A bulb is connected first dc and then ac of same voltage then it will shine equally with both .